1. Field of the Invention
The present invention relates to software protecting systems and more particularly to protection systems conformed to recognize and correct the most fundamental processing functions.
2. Description of the Prior Art
The advent of personal computers (PCs) has brought with it extensive snaring of data and programs. Thus, it is now a common practice to use commercial communication networks as a part of a personal computer system. Once tied to such a network, any PC resident system is susceptible to external modification.
Recently, the unauthorized access to a data processing system has grown as an item of vandalism and the term "computer virus" is now a generic term for program code selected to do mischief in a targeted system.
The variety of forms of such a virus is virtually unbounded. Of particular interest, however, are those viruses that destroy disk resident programs, as a matter of mischief. Most pernicious amongst the latter are "viruses" that inscribe directly onto the boot sector, i.e., viruses directed at the partition table of a disk. Since the boot sector and partition table are the first items of data in any "boot up" of a disk resident system, a virus in that location is virtually without any defense. Any disk operated system (DOS) relies on access to operating programs stored on a disk and the disk storage is defined by disk sector location, or the partition table. Thus, a virus inscribed at the "boot sector" cannot be corrected without major architectural reconfiguration of the hardware in the P.C.
This inherent dilemma in all disk operated systems has had few solutions in the past. These same aspects are an attraction to those bent on vandalism, and the virus species known as the "boot sector virus" is now a favorite item of mischief,
Defensive techniques for the boot sector virus are therefore extensively sought and it is one such technique that is disclosed herein.